The invention relates to an arc quenching apparatus for circuit breakers, based on a plate chamber construction. The apparatus comprises a quenching space in which each phase has a stationary contact and a knife contact pivotable in relation thereto, and which has a quenching chamber in whose body member, made of an insulating material, quenching plates are disposed in a spaced-apart relation so as to be located successively in relation to the path of the opening movement of the knife contact. The arc quenching installation according to the invention is particularly suitable for use in SF.sub.6 -insulated medium-voltage circuit breakers.
A basic construction of the kind described above is known, for instance, from the Applicant's earlier load circuit breaker of the type OETL 250 . . . 3150 (the FIGURES refer to ampere values), wherein the quenching plates are disposed in the form of a circular arc substantially perpendicularly to the tangent of the path of the knife contact.
Another extinguishing apparatus based on a plate chamber construction is known from European Patent 0 157 242. In this apparatus, a stationary contact and a quenching chamber are disposed on a busbar. The quenching plates of the quenching chamber are disposed in the chamber in parallel with the tangent of the starting point of the path of the knife contact and in a spaced-apart relation, and further superposed with an overlap so that the distance between the movable knife contact and the quenching plates increases as the opening movement of the knife contact proceeds.
The advantage with the quenching installations of the type described above, based on a plate chamber construction, is that the actual circuit breaking operation is successful with a small amount of energy. However, the problem with this apparatus has been found to be that the arc will produce a layer of soot on the quenching plate support structure made of an insulating material, and this soot layer will make the support structure conductive between the quenching plates. As a result, the breaking capacity of the circuit breaking apparatus is strongly impaired.